efs is unable to identify the remote host type ...

In XEmacs 20.4 "Emerald" [Lucid] (hppa1.1-hp-hpux10.20) of Thu Feb 25 1999 on shin

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

I got the following error message trying to dired on a remote IBM 
mainframe running z/OS (MVS):

   efs is unable to identify the remote host type of ...

   Please report this as a bug. It would be very helpful
   if your bug report contained at least the PWD command
   within the *ftp [email protected]* buffer.
   If you know them, also send the operating system 
   and ftp server types of the remote host.

A copy of the entire *ftp* buffer is appended.
The emacs-version is: "20.4 \"Emerald\" XEmacs  Lucid"
The efs-version is:   "1.15/1.56"

Thanks,
Peter
[email protected]
732 699-7370

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open pyaprod.cc.telcordia.com
Connected to pyibm9.cc.telcordia.com.
220-FTPSERVE IBM FTP CS V1R5 at PYIBM9.CC.TELCORDIA.COM, 06:28:07 on 2005-02-13.
220 Connection will not timeout.
quote user "tktfapk"
Remote system type is MVS.
ftp> 331 Send password please.
ftp> quote pass  Turtle Power!
230 TKTFAPK is logged on.  Working directory is "TKTFAPK.".
ftp> hash
Hash mark printing on (1024 bytes/hash mark).
ftp> quote pwd
257 "'TKTFAPK.'" is working directory.
ftp> pwd
257 "'TKTFAPK.'" is working directory.
ftp>